How to use Photoshop layer masks

Photoshop layer masks offer advanced control over image transparency, one of the most basic functionalities of Photoshop. Because of their fundamental nature, every Photoshop user should have a working understanding of layer masks and how to use them. They open huge doors to creative possibilities and help Photoshop users knock out simple tasks as well!

What is a Photoshop layer mask?
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Photoshop layer masks control the transparency of the layer they are “worn” by. In other words, the areas of a layer that are hidden by a layer mask actually become transparent, allowing image information from lower layers to show through.

To use a simple analogy, Photoshop layer masks work similar to masquerade ball masks. These masks hide some areas of a persons face and reveal others—often the eyes, nose and mouth. Similarly, Photoshop layer masks can be used to hide and reveal sections of a layer.

Why use layer masks?

I mean… can’t I just use the eraser tool to remove parts of an image? The answer is yes! However, if you do those parts of the image will be lost forever. That method resides in what we consider a destructive workflow.

Layer masks, on the other hand, leave the original layer pixel data untouched. This means you can play with the transparency in a multitude of ways without harming the layer content or creating an irreversible mess. With that said let’s jump in!

Layer mask tutorial

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Photoshop provides a complete set of functions for handling layer masks. Let’s start by adding a layer mask to a layer.

First, select the layer you want to mask (in this example Layer 1), then click the layer mask button as highlighted above. Alternatively, you can navigate to Layer > Layer Mask > Reveal All (we’ll get to the other options later). As seen in the example above, a white rectangle appears to the right of the image thumbnail.

Despite the fact that we’ve added a layer mask, nothing has visibly changed on the canvas. The reason for this has to do with the contents of the layer mask. That’s right, layer masks hold pixel data too! In fact, they can be thought of as layers in their own right, existing in a parallel universe.

Currently, the layer mask in our example holds entirely white pixels, as seen in the layer mask thumbnail. This means the areas of a layer mask that hold white pixels allow the same pixel area of their corresponding layer to show through.

Layer mask filled with black

What happens if we replace the layer mask’s white pixels with black pixels? Simply click the layer mask thumbnail, then click Edit > Fill. Let’s choose black. Instantly we see that the layer mask thumbnail turns black, and the corresponding layer disappears from the canvas – revealing the clouds in Layer 2!

Contrary to our previous example, which uses a layer mask filled with white pixels, layer masks filled with black pixels create full transparency in the corresponding pixel area of the layer which is masked.

Can you guess what happens if we fill half the layer mask with white and half with black? That’s right! Half the image becomes visible while the other half stays transparent. In this case, we would see half clouds and half bird.

Layer mask filled with gradient

Layer masks don’t end with black and white. In fact, layer masks can hold any form of grayscale pixel information. Let’s see what happens if we fill the layer mask with a gradient ranging from black to white!

Press G to switch to the gradient tool, then select the layer mask by clicking on its thumbnail. Finally, let’s drag the gradient tool across the canvas. As you can see, the thumbnail fills with a gradient from black to white and the corresponding layer smoothly transitions between full opacity and full transparency.

In essence, the clouds in Layer 2 are “showing through” the areas of Layer 1, which have become transparent as a result of the gradient layer mask.

Layer mask filled with photographic content

Let’s not stop there! If layer masks can hold any grayscale information, why not try to mask a layer with something photographic? In this example, we will try using a textural image of plaster to mask the word “Fade”, which we’ve set in a vintage cursive font.

To start, let’s create a layer mask on the “Fade” layer. Next, copy the contents of the plaster layer by clicking its thumbnail, then pressing Ctrl/Command + A to select all, then Ctrl/Command + C to copy.

To paste this image into the layer mask on the plaster layer we need to enter into the “parallel universe” of the layer mask and we do that by holding alt/option then clicking the layer mask thumbnail.

Now, the canvas displays the contents of the layer mask. Cool, huh? Paste in the plaster image by pressing Ctrl/Command + V.

To escape this “parallel universe” (isn’t this fun?), simply click the layer thumbnail (the capital “T” symbol). Great! Now “Fade” has a plaster texture that lets some of the colored background show through.

You can fine tune the layer mask by clicking the layer mask thumbnail again and selecting Image > Adjustments > Brightness & Contrast. Perfect! What we love about this technique is that it lets the layer below, in the case a warm orange color fill, show through the textural variance.

The chain-link

You may also be wondering what that chain-link is doing between the layer thumbnail and layer mask thumbnail? Quite simply, this chain-link means that if you move the layer image on the canvas, the layer mask will move around with it.

This can be incredibly useful. For example, if you’ve carefully cut out the background of an image and need to reposition it on the canvas. Otherwise, you might be experimenting, trying to find the perfect area of a pattern to “let through” a layer mask. In this case you would want to disable the chain-link. That’s easy! Just click it.

Conclusion

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Now you should feel like you have a better understanding of layer masks! Bringing this tool into your workflow will make you a better Photoshop user based on your increased facility to enter into new creative possibilities!

Masks can be applied to any layer no matter what order they are in. Do you mean to ask how to use a mask to reveal part of another image on another layer? In that case, applying white to a mask will reveal all layers beneath the mask (if it is solid white, the masks layer will have no transparency). If you are trying to make the current layer that the mask is on partially transparent to reveal the layer underneath, that layer does have to be directly below the mask.

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